Microstructure and mechanical behaviour of transient liquid phase spark plasma sintered B4C–SiC–TiB2 composites from a B4C–TiSi2 system

Abstract

Almost fully-dense B4C–SiC–TiB2 composites with a high combination of strength and toughness were prepared through in situ reactive spark plasma sintering using B4C and TiSi2 as raw materials. The densification, microstructure, mechanical properties, reaction, and toughening mechanisms were explored. TiSi2 was confirmed as a reactive sintering additive to promote densification via transient liquid-phase sintering. Specifically, Si formed via the reaction between B4C and TiSi2 that served as a transient component contributed to densification when it melted and then reacted with C to yield more SiC. Toughening mechanisms, including crack deflection, branching and bridging, could be observed due to the residual stresses induced by the thermoelastic mismatches. Particularly, the introduced SiC–TiB2 agglomerates composed of interlocked SiC and TiB2 played a critical role in improving toughness. Accordingly, the B4C–SiC–TiB2 composite created with B4C-16 wt% TiSi2 achieved excellent mechanical performance, containing a Vickers hardness of 33.5 GPa, a flexural strength of 608.7 MPa and a fracture toughness of 6.43 MPa m1/2.